Production of trialkylboranes



. same kind.

United States Patent PRODUCTION OF TRIALKYLBORANES John C. Perrine, Jr., Pasadena, Calif., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia No Drawing. Application July 29, 1957 Serial No. 675,515

4 Claims. (Cl. 260-6065) This invention relates to a method for the production of trialkyl boranes of the type RRR"B wherein R, R and R are lower alkyl radicals, particularly those containing from 1 to 4 carbon atoms. As is described in U. S. Patent No. 2,266,776, to Leum, such trialkyl boranes, in the form of amine addition products, are useful additives to diesel fuels and the like for the purpose of increasing their cetane number. In addition, such trialkylboranes are useful for the purpose described in Klein, Nadeau, Schoen and Bliss application Serial No. 614,768, filed October 8, 1956.

In accordance with the present invention, the trialkylboranes are produced by reacting a trialkylboroxine (11 E 0 and a compound of the class RAlXX. R and R are alkyl radicals containing from 1 to 4 carbon atoms, and X and X are alkyl radicals containing from 1 to 4 carbon atoms or are halogen atoms, particularly iodine, bromine and chlorine. Thus, R'AlXX' can be a trialkyl aluminum compound, such as aluminum trimethyl or aluminum triethyl, or it can be an alkyl aluminum halide, such as methyl aluminum di-iodide or dimethyl aluminum monoiodide. If desired, by appropriate choice of the reactants, it is possible in accordance with the method of the present invention to prepare mixed trialkylboranes or, on the other hand, it is possible to prepare trialkylboranes wherein each alkyl radical is of the In carrying out the reaction, the relative proportions of trialkylboroxine and RAlXX' can be varied widely. Preferably, however, the ratio of the number of alkyl radicals introduced into the reaction zone in the RAlXX to the number of boron atoms introduced into the reaction zone in the trialkylboroxine is within the range from 0.5 to 8. In other words, the amount of R'AlXX' employed can be from one-fourth to four times that stoichiometrically required to convert the boron in the trialkylboroxine to a trialkylborane. The reaction between the trialkylboroxine and R'AIXX' is generally carried out at a temperature within the range from about 0 C. to 150 C., although somewhat higher and somewhat lower reaction temperatures can also be used. After the reaction has been carried out to produce the trialkylboroxine, the desired product can be separated from the reaction mixture using conventional means, particularly by precise fractionation of the reaction mixture.

The following examples illustrate various embodiments which fall within the scope of this invention.

Example I 3 cc. of tributylboroxine was placed in a tube having a capacity of about 50 ml. fitted with a stopcock. The

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tube was immersed in a liquid nitrogen bath whereby it was cooled to -196 C., and was then evacuated. 1.5 grams of aluminum trimethyl was condensed into the tube containing the tributylboroxine. As the tube was allowed to warm to room temperature, a very violent reaction took place. The volatile material present in the tube was collected in a trap cooled to l96 C. An infrared spectrum of this volatile material showed that the product was butyl dimethylborane. The butyl dimethylborane obtained weighed 2.75 grams.

Example 11 Aluminum methyl iodide (composed of approximately equal amounts by weight of CH AlI and (CH AlI), 5 cc. was placed in a 35 cc., S-necked flask fitted with a pressurized funnel, reflux condenser and stopper. Tributylboroxine, 5 cc., was placed in the addition funnel. The top of the reflux condenser was connected to a vacuum source through a trap immersed in liquid nitrogen. The flask was then immersed in liquid nitrogen and evacuated. The liquid nitrogen bath was then removed from the flask and the flask was permitted to warm up to room temperature. The tributylboroxine was added dropwise to the aluminum methyl iodide and an exceed ingly violent reaction took place, occasionally accompanied by incandescence. After the conclusion of the reaction, the flask was warmed for ten minutes by immersion in a beaker of boiling water.

The material that volatilized was collected in a trap cooled to 196 C., this material was shown to be butyl dimethylborane by vapor density, boron alalysis and boron and nitrogen analyses of its pyridine adduct. The yield was 90 percent, based upon the methyl content of the methyl aluminum iodide. The theoretical analysis calculated for butyl dimethylborane is 11.1 weight percent of boron and the calculated molecular weight is 98. The butyl dimethylborane obtained in this reaction contained 11.5, 11.4 weight percent boron and had a molecular weight of 100, 102. The butyl dimethylborane isolated as the reaction product weighed 2.0 grams and had a vapor pressure between mm. and mm. of mercury at room temperature.

What is claimed is:

l. A method for the production of a trialkylborane which comprises reacting a trialkylboroxine of the formula R B O and a compound of the class RAlXX' at a temperature within the range from about 0 C. to about C., R and R being alkyl radicals containing from 1 to 4 carbon atoms, X and X being selected from the group consisting of halogen atoms and alkyl radicals containing from 1 to 4 carbon atoms, and the ratio of the number of alkyl radicals introduced into the reaction zone in the R'AlXX' to the number of boron atoms introduced into the reaction zone in the trialkylboroxine being within the range from 0.5 to 8.

2. The method of claim 1 wherein X and X are alkyl radicals.

3. The method of claim 1 wherein X and X are iodine.

4. The method of claim 1 wherein RAlXX is trimethylaluminum.

No references cited. 

1. A METHOD FOR THE PRODUCTION OF A TRIALKYLBORANE WHICH COMPRISES REACTING A TRIALKYLBOROXINE OF THE FORMULA R3B3O3 AND A COMPOUND OF THE CLASS R''AIXX'' AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 0*. TO ABOUT 150*C., R AND R'' BEING ALKYL RADICALS CONTAINING FROM 1 TO 4 CARBON X AND X'' BEING SELECTED FROM THE GROUP CONSISTING OF HALOGEN ATOMS AND ALKYL RADICALS CONTAINING FRO 1 TO 4 CARBON ATOMS, AND THE RATIO OF THE NUMBER OF ALKYL RADICALS INTRODUCED INTO THE REACTION ZONE IN THE R''AIXX'' TO THE NUMBER OF BORON ATOMS INTRODUCED INTO THE REACTION ZONE IN THE TRIALKYLBOROXINE BEING WITHIN THE RANGE FROM 0.5 TO
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